Yes of course!  For instance, even in a non-aqueous solvent like DMF Copper (I) Acetate can accept an electron and become Copper (II).  Look up your 'Lewis' theory on electron donation/acceptance in pH.

It depends on the metal ion you are talking about. Some metal ions are oxidizing and some are not. Which ones are you using?

As Khaleel said above, depends on the metal.

thank you all for your suggestions. Actually i have a ligand that doesn't have any metal when i am refluxing it in DMSO with Nickel acetate then nickel is cordinating to the ligand and ligand itself oxidizing